[Greenbuilding] Swedish solar-heated village

[John Daglish]

Our Dannish friends are way ahead...

Smart Energy Systems: 100% Renewable Energy at a National Level (Short Version)
https://www.youtube.com/watch?v=S1P31EC0YsE

Smart Energy Systems: 100% Renewable Energy at a National Level (Full Version)
https://www.youtube.com/watch?v=eiBiB4DaYOM

Solar heat fields for district heating   - real time production
statistics, not much today its cloudy
http://www.solvarmedata.dk/

regards

John Daglish
Paris, France




John Daglish
Paris, France


2015-11-25 21:11 GMT+01:00 Dan Johnson <danjoh99 at gmail.com>:
> It's great to see Nick Pine back on this list. I want to point out for
> discussion that the electrical grid has virtually no storage! The grid
> follows load and must be balanced nearly instantaneously with dispatchable
> generation.
>
> Contributing PV energy to the grid is often part of the problem, because
> renewables often need to be curtailed when production exceeds demand. Grid
> operators can't taper down the baseload generators every time the wind picks
> up. The California ISO site has a lot of current information and I've found
> it a great place to learn about the electrical grid. And this is one of the
> most progressive operators in terms of their renewables and storage mandates
> from the State. http://www.caiso.com/Pages/default.aspx
>
> Bringing this back to solar storage in winter (in California, for example),
> when I do morning warm-up or heat during a cloudy day using my electric
> heat-pump, the electric grid is running natural-gas-fired generators at an
> emissions rate that is dirtier than average. This is because renewables are
> generally not online during these periods. Check out this net-demand chart
> from Cal ISO: the morning peak of the green line is all fossil fuel, before
> solar comes online. http://content.caiso.com/outlook/SP/duck.gif. There may
> be less emissions and less fuel burned if I just burned the natural gas at
> my house with a condensing appliance, as a backup to my passive systems,
> using no storage. The chemical bonds in the natural gas provide the storage.
> :-)
>
> Any net surplus of PV from my house would occur when I don't need it to
> power a heat-pump or A/C: these are periods when likely other houses don't
> need it either. Net consumers would be commercial buildings, hospitals, and
> other process loads on the grid. In one scenario, we can ramp-down the
> fossil generators during these periods, so **here is where we can argue that
> the homeowner's PV could be considered a carbon offset**---but no more real
> than Terrapass. http://www.terrapass.com/. In another scenario, the added
> power from renewables just lets us bring more loads online---total load and
> demand grow over time! This is the opposite of what we wanted.
>
> Returning to grid-scale storage: it seems this is science fiction, like
> clean coal. Euan Mearns has some great analysis of experimental pumped hydro
> schemes in the Canary Islands.
> http://euanmearns.com/el-hierro-another-model-for-a-sustainable-energy-future/.
> California conducted a workshop in Jan 2014 on pumped storage and many
> presentations from it are here:
> http://www.cpuc.ca.gov/PUC/energy/electric/Technical_Workshop_Understanding_Current_State_of_Pumped_Storage.htm.
> If 300 high reservoirs were built along the coast, using the ocean as the
> low reservoir, the grid could get 572 GWh of storage, almost 1 day of
> storage for California!
> http://www.cpuc.ca.gov/NR/rdonlyres/1521FE3B-2FB5-4A6A-A93B-45125D6EF895/0/Barnhart20140116CPUCPHSWorkshop.pdf
>
> Best,
> Dan Johnson
> Albany, CA
>
> On Tue, Nov 17, 2015 at 12:06 PM, Nick Pine <nick_pine at verizon.net> wrote:
>>
>> Kimmo writes:
>>
>>> I’m an entrepreneur that is doing research the possibility to use some
>>> architecture ideas to heat houses in Sweden similar
>>
>> to what Soldiers Grove did back in 1979. We will of-course try to
>> modernise the design but the basic concepts are the same
>> with the “solar attic”.
>>
>> Soldier’s Grove attics required moving warm air down to the lower part of
>> the building using fans or blowers and a motorized damper, and it’s hard to
>> store solar heat from warm air. I figure cloudy days are like coin flips, so
>> a building that can store enough heat for 1 cloudy day can be at most 50%
>> solar heated, with a possible max 1-2^-N solar heating fraction if it can
>> store enough solar heat for N cloudy days in a row, eg 1-2^-5 = 0.97 with 5
>> days of storage. Most of the SG buildings were only 50% solar heated. Why
>> stop there?
>>
>> It seems to me that collecting enough heat to warm a building on an
>> average day would be simpler with some passive solar heaters built into the
>> south wall, eg
>> http://www.builditsolar.com/Projects/SpaceHeating/solar_barn_project.htm
>>
>> Where I live near Philadelphia, PA, 1000 Btu/ft^2 of sun falls on a south
>> wall on an average 30 F January day, so a 4 foot x 8 foot vertical south air
>> heater with US R2 twinwall polycarbonate glazing with 80% solar transmission
>> would gain 0.8x32ft^2x1000 = 25.6K Btu/day. With a 70 F building and a T (F)
>> exit air heater temp and a (70+T)/2 average air temp inside the heater and a
>> 6-hour solar collection day, the heater would lose about
>> 6h((70+T)/2-30)32ft^2/R2 = 48T+480 Btu/day. With a constant C cfm airflow,
>> the collector would provide 6C(T-70) Btu/day of heat to the building... 2 1
>> ft^2 vents with one-way plastic film flappers and an H = 8 foot height
>> difference would make C = 16.6x1ft^2sqrt(8'(T+70)/2-70)) =  33.2sqrt(T-70)
>> cfm, and 25.6K = 48T + 480 + 200(T-70)^1.5 makes 543 = T + 4.15(T-70)^1.5,
>> ie T = 70+((543-T)/4.15)^(2/3). Plugging in T = 100 on the right makes T =
>> 92.4 on the left, then 92.7, then 92.7, with C = 158 cfm and a
>> 6x158(92.7-70) = 21.5K Btu/day heat gain for the building, which might have
>> just enough thermal mass and insulation and airtightness to cool from 70 to
>> 60 F by dawn... 60 = 30+(70-30)e^(-18h/RC) makes RC =
>> -18h/ln((60-30)/(70-30)) = 63 hours.
>>
>> And given the present low cost of PVs and inverters, we might heat the
>> building with Mitsubishi or Fujitsu mini-split heat pumps on cloudy days
>> (they work with an outdoor air temp down to minus 13 F), powered by PVs,
>> using the electrical grid for storage instead of a 5000 gallon hot water
>> tank. How many peak watts of PV would be required for space heating alone,
>> with a COP of 3? A simulation using hourly EPW weather data could help
>> estimate this.
>> http://apps1.eere.energy.gov/buildings/energyplus/cfm/weather_data3.cfm/region=6_europe_wmo_region_6/country=SWE/cname=Sweden
>>
>> Then again, a solar village could have passive solar air heaters on each
>> house and a large common underground heat storage tank with a geodesic
>> transparent roof and a simple drainback hydronic collector on top of a
>> floating insulated cover under the roof.
>>
>> Nick
>>
>>
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>
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